# What is the H^+ concentration for an aqueous solution with pOH of 4.31 at 25°C?

Well, clearly $p H = 9.69$
Why clearly? Because $p O H + p O H = 14$ in aqueous solution under standard conditions....
$\left[{H}_{3} {O}^{+}\right] = {10}^{- 9.69} \cdot m o l \cdot {L}^{-} 1 = 2.04 \times {10}^{-} 10 \cdot m o l \cdot {L}^{-} 1$.